MortenM... your input was dismissive and insulting (using the 'loser' smiley to end your post is completely inappropriate)... I'm seeking answers, not attitude... and it was going along well until now.

 

Excuse me, but if I recall correctly you brought the attitude into this discussion;

 

Yeah... ok... but as a developer I read it this way: "X-Plane does not calculate weight and balance."

 

I'm really not seeing where RoG provides accurate flight performance with regards to weight and balance at all.

 

And, I answered your questions including the ones you asked after that.

 

M

Tom,

 

I see no entry for the reference datum point. Also, many aircraft have more than 8 seats. Does this mean for X-Plane you have to ignore that and never go beyond the 8?

 

One aircraft I'm looking at in PlaneMaker has the CoG entry on the WEIGHT & BAL tab filled with identical values for forward, default and aft limits... fuel tank entries sitting at the same position as the CoG on the WEIGHT & BAL tab and then on the CG SET tab has an entry for 'empty craft' and another for 'fuel'. This honestly makes no sense as it comes across as duplicate entries.

Ok,

 

so, we can all reach the same conclusion, I believe. In MSFS we use MOIs, while in xplane ROG are used. Both simulators also use CoG calculations based on a default CoG reference point adapted to loads at various "load stations" or whatever we want to call it.

 

I believe the rest is up to the FM, both in MSFS and XPlane. Although I only played with ROIs in xplane9 helicopters, I remember that I also used to modify it on many aircraft models (specially gliders) in MSFS :-), and on both sims it was possible to get much better results...

 

Thanks for the important info already gathered in this thread!

I see no entry for the reference datum point. Also, many aircraft have more than 8 seats. Does this mean for X-Plane you have to ignore that and never go beyond the 8?

 

The reference point is just a 0, 0, 0 point in space. Everything in PM, geometrically, will be defined within this cartesian coordinate space. It will be represented in PM by a black dot (and so will lots of other points, which I agree is annoying). Regarding the seats...you are implying that you want one Cg entry per seat? That's not terribly practical, what would you want if you did a 777? Now 10 - 20lb seats with their collective center 200" from a datum is the same as 1 - 200 lb seat at that same center...and you only need 1 entry to put it in...so a bit of "equivalent moments" is in order here...OR since seats don't move, you can wrap those values into the default RoG value (assuming you did not want to simulate removing them) and leave the variable load slots open for other things. Inside the x-plane folder is a great PDF manual called "Plane-Maker_10_manual.pdf". Page 11 of that manual specifically addressed, "The reference point". It's 84 pages of goodness and I get the impression you might not have looked through it yet. I think you should browse over and and you will probably find lots of answers to your questions Ed.

 

Regarding the aircraft you were looking at, indeed it sounds like those are some "amateurish" settings and as I mentioned in a previous post somewhere, the onus for a good flight model is on the aircraft author moreso than x-plane itself.

 

Tom

I was talking about seats because they fill with passengers/crew. While for a 777 it may be a non-issue... for a smaller business jet, individual passenger weights and their positions can be critical, especially in one loaded towards maximum.

Ah, I see Ed. Well in such a case with more than 8, I would probably treat any "side by side" passengers as one entry...possibly even group 4 together if need be.... and add their weights together, thereby saving some of the weight "slots". The lateral moments are probably insignificant compared to the longitudinal ones, especially the more seats you have. The downside to this arrangement though is the configuration is "fixed" and does not represent "variable loading" without modifying the original aircraft file. It is in this "customization" situation where some plugin-programming would be called for. Some add-ons are doing it, though whether or not they are affecting the weight and balance properly for their custom configuration is unknown.

 

Tom

Ah, a topic that exemplifies what a forum topic should be! So esoteric that it can't possibly break out into fisty-cuffs, and one which will allow me to go play MECHWARRIOR II safe in the knowledge that love, peace and harmony have broken out all over the place! My one good nerve has been holstered! :Party:

Ok... that's a limitation... but one that may be worked around... I'd have to do some deep thinking.

 

Next thing... fuel. No way to physically connect to a specifric tank? Once again, certain aircraft have rather unique fuel systems.

LOL! That's awesome, Tom A!

Next thing... fuel. No way to physically connect to a specifric tank? Once again, certain aircraft have rather unique fuel systems.

 

X-Plane has up to 9 fuel tanks you can use, each with it's own location. The general idea here is to better model mass effects on wing tanks....not get really wild fuel transfer scenarios. It used to be that x-plane only had 3 tanks. When it comes to managing fuel transfer though, the options get very limited. I have to admit, I am not sure of the options as I tend to do custom plugin programming to manage fuel between tanks....at least on the MU2, I did. I think if you have a "off /right / left / both" situation, then x-plane can handle that well. You can also specificy fuel tank pressure to force an "order" of fuel tank depletion...but only in the absence of explicitly setting a tank to use with one of the fuel selector gauges. It would take some experimentation probably to figure this one out. If you go to plane-makers' panel editor and look in "buttons > fuel"...then you can mouse over some of the fuel transfer buttons and see what options exist. I will say that matching up the "fuel tank ID numbers" on the fuel selector buttons vs. which tank in planemaker it actually connects to is a royal pain. I don't have any hard and fast rules of thumb here Ed. Sorry.

 

Tom